The present invention relates to a variable displacement swash plate type compressor adapted for use in an air conditioning system for a vehicle, and more particularly to a compressor having a passage in a drive shaft for providing lubricating oil to the crankcase.
A typical conventional variable displacement swash plate type compressor includes a cylinder block provided with a number of cylinders, a piston disposed in each of the cylinder of the cylinder block, a crankcase sealingly disposed on one end of the cylinder block, a cylinder head sealingly disposed on the other end of the cylinder block, a rotatably supported drive shaft, and a swash plate. The swash plate is adapted to be rotated by the drive shaft. Rotation of the swash plate is effective to reciprocatively drive the pistons. The length of the stroke of the pistons is varied by the inclination of the swash plate. Inclination of the swash plate is varied by controlling the pressure differential between a suction chamber and a crank chamber. The pressure differential is typically controlled using a control valve and a conduit formed within the cylinder block which provides fluid communication between a discharge chamber and the crank chamber to convey compressed gases from the discharge chamber to the crank chamber based on the pressure in the suction chamber. The conduit also typically provides communication for lubricating oil between the discharge chamber and the crank chamber to achieve lubrication of the moving components within the crank chamber.
Another conventional lubricating system disclosed in the prior art employs a forced lubrication system including an oil pump provided at one end of the drive shaft and driven by the drive shaft to lubricate the moving components within the crank chamber. The forced lubrication system typically causes lubricating oil to be pumped from an oil sump, through a pump chamber, a lubrication passage and radial branch passageways within the drive shaft, to the crank chamber.
The compressor arrangements in the prior art described above have several disadvantages. First, when a compressor having a conduit within the cylinder block is operating at minimum capacity, ineffective lubrication of the close tolerance moving parts within the crank chamber occurs due to the lack of consistent flow of refrigerant gas from the discharge chamber to the crank chamber. Second, in a compressor having a forced lubrication system, the compressor may include an oil sump, a pump chamber, and an oil pump operatively connected to the drive shaft adding expense.
An object of the present invention is to produce a swash plate type compressor wherein oil flow to the crankcase during both minimum and maximum operating conditions is improved to result in efficient lubrication of the compressor components.
Another object of the present invention is to produce a swash plate type compressor wherein the oil sump, the pump chamber, and the drive shaft driven oil pump of the prior art can be eliminated.
The above, as well as other objects of the invention, may be readily achieved by a variable displacement swash plate type compressor comprising: a cylinder block having a plurality of cylinders arranged radially therein; a piston reciprocatively disposed in each of the cylinders of the cylinder block; a cylinder head attached to said cylinder block and having a discharge chamber formed therein; a crankcase attached to the cylinder block to define a crank chamber; a drive shaft rotatably supported by the crankcase and the cylinder block; a swash plate adapted to be driven by the drive shaft and having a central aperture for receiving the drive shaft, radially outwardly extending side walls, and a peripheral edge; and a lubrication passage formed within the drive shaft providing fluid communication between the discharge chamber and the crank chamber.